This invention relates to a gas absorption process for the removal of acidic components, especially CO.sub.2 and H.sub.2 S and, in some cases, COS, from CO.sub.2 -rich, hydrocarbon-containing raw gases wherein the raw gas is scrubbed under pressure with a physical scrubbing medium selective for H.sub.2 S and COS; and the resultant loaded scrubbing agent is then regenerated and reused.
Is is conventional to remove sour gases, e.g., CO.sub.2, H.sub.2 S, and COS from gaseous mixtures by the use of scrubbing processes. In this connection, physical, i.e., no chemical reaction, scrubbing procedures have been utilized as well as chemical. The physical scrubbing processes operate most efficiently under a high total pressure and with a high sour gas concentration. However, a disadvantage with physical scrubbing processes occurs when there is the simultaneous presence of hydrocarbons which have a similarly high solubility as the sour gases in the scrubbing agent.
Physical scrubbing processes already in use employ, e.g., as the absorbents, polyethylene glycol ether, N-methylpyrrolidone, or propylene carbonates (e.g., Oil and Gas Journal No. 40, October 1982, pages 90-93). In most cases, these scrubbing processes are employed to remove the acidic components from natural gases to such an extent that the purified gas can subsequently be utilized as fuel gas. Usually, H.sub.2 S from the sour gases is reacted to elemental sulfur and the CO.sub.2 is exhausted into the atmosphere.
Besides the use of scrubbing methods, sour gases are removed from gaseous mixtures by liquifaction and subsequent rectification. To avoid precipitation of CO.sub.2 durint cooling and rectification, it is suggested in the prior art to add a suitable solvent, such as a lighter hydrocarbon, preferably propane. In this way, CO.sub.2 and H.sub.2 S can be separated by rectification into H.sub.2 S-free CO.sub.2 and into concentrated H.sub.2 S and solvent. A serious disadvantage of this process, however, resides in that H.sub.2 S and the above-mentioned solvent cannot be economically separated cleanly from each other by rectification. Accordingly, a chemical scrubbing step must be used to remove the H.sub.2 S from the vaporized solvent. This involves the drawback that a relatively large amount of vapor must be used for the regeneration of the liquor, and, simultaneously, the solvent required for rectification must additionally be subjected to a drying step. Such a process is described e.g. in the paper presented at 61st Annual GPA Convention March 15-17, 1982, Dallas, Tex.